Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$216.42	5.152%	$227.57	$227.57	$227.55	$227.60
Purchase #2	$152.78	8.421%	$165.6456	$165.65	$165.65	$165.60
Purchase #3	$195.44	9.162%	$213.3462	$213.35	$213.35	$213.30
Purchase #4	$54.87	12.745%	$61.8632	$61.86	$61.85	$61.90
Purchase #5	$136.89	3.429%	$141.584	$141.58	$141.60	$141.60
Purchase #6	$90.60	10.608%	$100.2108	$100.21	$100.20	$100.20
Purchase #7	$119.37	8.272%	$129.2443	$129.24	$129.25	$129.20
7 purchase totals =	$966.37		$1,039.4641	$1,039.46	$1,039.45	$1,039.40